Artesian Spring not well for N.O.

Artesian Spring not well for N.O.

I’ve been watching some of the Fox News Channel coverage of the current situation in New Orleans.

Sheppard Smith, in particular, was commenting on the fact that flood waters are rising in the city. Some of this appears to be caused by some known partial breeches of the levee system. But Smith said many observers were convinced that there must be some additional mechanism involved. This could be something as simple as leaks in levees below water level on both sides – these would have to be rather slow leaks to not cause turbulence that would be spotted from the helos that are flying recon.

I’m not a hydrologist or geologist, but I did take “rocks” as my required lab science at UVa; so, I have a few musty concepts in the back of my head and a lot of intellectual conceit.

Let’s give this puzzle a try.

1. FACT: Much of New Orleans, and all the part Smith was talking about this morning, is below sea/river level.

2. GUESS: New Orleans is built, at least in part, on unconsolicated alluvial material.

3. FACT: For centuries, human occupancy of New Orleans has depended on a complex system of levees to keep out the river and pumps to get rid of rainfall and sewage.

4. FACT: The hurricane has added an appreciable amount of water all over the area – the River, Lake Pontchartrain, the bayous, etc.

My conclusion? Water is seeping up into the city. This would be happening even if there were no damage to the levees. This may have been going on all the time, perhaps with the pump operating authority being aware of it, or perhaps not.

The key changed variable from normal operations in New Orleans is that pesky point 4 - increased the hydrostatic pressure pushing in on the city transmitted through subsurface waters. Think of New Orleans as a very large ship attached to the bottom of a shallow sea. If you raise the water level around the hull, the pressure at the lowest point rises – maybe to a point where little cracks that were annoying seasonal wet spots become sprays of water entering the hull.

Now, remember that New Orleans is not a ship with a solid hull. This brings us to point 2 – which means that at some level the groundwater within the levee system is connected to the groundwater outside the levees. So, some of that excess water from Katrina may be making itself felt inside the city by upwelling from below.

It’s just a thought. Only time will tell.